End transformer and enclosure

ABSTRACT

An end enclosure for transformers in which a pair of opposed transverse walls are formed along bend lines which form a square corner with the top wall, said sidewalls having elongated openings which extend up to said bend lines to provide greater access space for conductors. The opposite pair of transverse walls may have top round corners so that said walls tend to counter displacement towards each other. Interlock means may be provided between the first and second pair of sidewalls to prevent outward displacement of the round corner sidewalls and inward displacement of the square corner sidewalls. A method for making such improved end enclosures from planar, deformable sheet material provides removing areas of selected configuration from the four corners of the sheet material, and forming the opposed pair of extending sidewall portions into the sidewalls of the enclosures by moving them along bend lines. A substantially continuous flange portion is formed by moving a bottom portion of each sidewall along bend lines.

United States Patent 11 1 Franz et al.

[ 1 Oct. 2, 1973 END TRANSFORMER AND ENCLOSURE [75] Inventors: Robert W. Franz, Elk Grove Village; John J. Zielnicki, Northbrook, both of I11.

[73] Assignee: Cam-Fran Tool Co., Inc., Chicago,

Ill.

[22] Filed: Jan. 3, 1972 [21] Appl. No.: 215,058

52' us. (:1 112 339, 113/116 P 51 int. c1 1121a 38/00 [58] Field of Search 72/339, 379, 335,

72/336; 336/90; 113/116 P, 116 V, 116 HH, 116 QA, 116 Y, 120 E, 120 HA, 120 UE Primary ExaminerCharles W. Lanham Assistant ExaminerRobert M. Rogers Attorney-Dominik, Knechtel & Godula [57] ABSTRACT An end enclosure for transformers in which a pair of opposed transverse walls are formed along bend lines which form a square corner with the top wall, said sidewalls having elongated openings which extend up to said bend lines to provide greater access space for conductors. The opposite pair of transverse walls may have top round corners so that said walls tend to counter displacement towards each other. lnterlock means may be provided between the first and second pair of sidewalls to prevent outward displacement of the round corner sidewalls and inward displacement of the square corner sidewalls. A method for making such improved end enclosures from planar, deformable sheet material provides removing areas of selected configuration from the four corners of the sheet material, and forming the opposed pair of extending sidewall portions into the sidewalls of the enclosures by moving them along bend lines. A substantially continuous flange portion is formed by moving a bottom portion of each sidewall along bend lines.

15 Claims, 15 Drawing Figures PATENTED 2l973 sum 10! 3 PATENTED HUI 21973 SHEET 2 BF 3 PATENTED UN 2 I975 3.762.205 sum aur 3 E wE END TRANSFORMER AND ENCLOSURE This invention relates to new end enclosures for transformers, and to a method for making such end enclosures. The invention particularly relates to an improved end enclosure which can be provided with one or more elongated openings that extend up to the junction or bend line between the sidewall and top wall of the enclosure. The invention further relates to a highly efficient and economical method for making such improved enclosures includinga continuous, automated method wherein such enclosures are formed along an advancing strip of deformable material.

End enclosures for transformers are now commonly made by a draw die wherein a sheet of deformable material forms a unitary structure having a top wall, sidewalls, and a substantially continuous flange at the bottoms of the sidewalls. Such enclosures are formed by a die element which deforms the sheet material around an anvil to obtain an enclosure with uninterrupted top walls, sidewalls and base flange.

Elongated openings are then punched out of the sidewalls of such enclosures by die punches which, however, must clear the anvil element inside the enclsosure. Such an anvil element understandably takes up space below the top wall, thereby preventing upper portions of the sidewalls from being perforated by the punch die. As a result, the elongated openings do not extend up to the junction line with the top wall. Such limited height of the elongated openings provides a smaller space through which conductors are down from the transformer for connections with other electrical components. The art has recognized that such limited heights of the openings results in often tightly bending the conductors, or constraining them within small spaces prior to drawing them through the openings. This has led to the very serious problem of damage to the insulator coating of the conductor, thereby causing shorts and fires. The known techniques in the art for making such end enclosures for transformers are inadequate to solve the problem of limited height of the elongated openings or slots for the conductors. So long as the anvil element must be positioned within the enclosure in the deformation and punching step, a certain upper portion area of each sidewall cannot be available for formation of the elongated opening. Such elongated openings customarily have an upward closed end which must be formed below the die element, that is, substantially below the top wall or the junction of the sidewall with the top wall.

The problem of limited height of the elongated opening occurs no matter which sidewall of the enclosure is selected. Such elongated openings are customarily formed on each of the four sidewalls, commonly two openings in each sidewall. Every opening must, of necessity, have its closed end positioned substantially below the top planer wall to thereby limit the available space of the opening.

The prior art unitary enclosures have the disadvantage of shortened openings, and have other disadvantages associated with their otherwise desirably, rigid structure. The unitary structure results in a lack of versatility in the formation process because such an enclosure can be formed essentially only by a draw die process over an anvil element. This seriously limits or eliminates the introduction of economical steps or innovations in the process which would tend to lead to the production of end enclosures in a more rapid and economical way.

It is accordingly one important object of the present invention to provide an improved end enclosure for transformers, and a method for making same, wherein sidewalls of the enclosure can have one or more elongated openings for conductors, which height is not limited in the sidewall areas. In this way, an end enclosure of given height can lead to elongated openings providing more available space through which conductors can be passed with consequent reduction in constraining movements of such conductors.

Another important object of the present invention is to provide an improved end enclosure, and method for making same, in which a rugged, operable end enclosure has separable sidewall portions which are moved along bend lines to form sidewalls lying in planes substantially normal to the top wall portion, at least some of such bend lines being square cornered.

Another important object of the present invention is an improved end enclosure for a transformer, and a method of making same, wherein an operable end en closure is formed from a planer sheet of deformable material in which separate sidewall portions extend in coplaner fashion from a top wall portion, and wherein elongated slot openings are formed in the sidewall portions while the sheet material is in planer disposition so that the closed ends of such elongated openings can be formed higher in sidewall areas.

Yet another important object of the present invention is an improved end enclosure, and method for making same, wherein one pair of separated sidewall portions can be formed with square corners, and another pair of sidewall portions can be formed with bend lines following a radius to impart greater rigidity against displacement of said radiused sidewalls.

Yet still another important object of the present invention is an end enclosure for transformers, and a method for making same, wherein separated sidewall portions can be efficiently moved by forming elements into sidewall positions in planes substantially normal to the top wall portion, and wherein such moved sidewall portions can be efficiently interlocked to counter tendencies against inward displacement of one pair of sidewalls and outward displacement of the other pair of sidewalls.

Still yet another important object of the present invention is an improved method for making end enclosures for transfonners wherein strips of deformable sheet material are advanced through progressive die stations so that sidewall portions, flange portions, and elongated openings may be speedily formed to obtain the completed, assembled and interlocked end enclosure following discharge from a last cutoff station.

Still yet another important object of the present invention is to provide an improved method for making end enclosures for transformers wherein a continuous advancing strip of deformable sheet material can be advanced through progressive die stations to bilaterally form enclosures on each side of a central carrier strip portion so that asingle strip can be used to increase end enclosure production.

Yet still another important object of the present invention is to provide an improved method for making end enclosures for transformerswherein a plurality of elongated openings can be punched out on each of four sidewall portions while such sidewall portions are disposed in coplaner fashion with a central top wall portion. Some of said openings have closed ends at about square corner bend lines and others have closed ends within the radius of bend lines, all of the closed ends of said elongated openings being formed without restricting their placements as a result of the forming elements used in the process.

The foregoing objects are now attained by the present invention shown in the following disclosure. Still other objects may be attained as they occur to practitioners from time to time upon considering such disclosure while includes drawings, wherein:

FIG. 1 is a perspective view showing the improved end enclosure of the present invention mounted in a transformer;

FIG. 2 is a perspective view of the end enclosure, on a reduced scale;

FIG. 3 is a perspective view showing the inside of the end enclosure of FIG. 2;

FIG. 4 is a sectional view of the end enclosure, on a reduced scale, taken along a plane following the short axis of the end enclosure shown in FIG. 3;

FIG. 5 is a plan view of a planer deformable sheet material blank used to form the end enclosure shown in the foregoing views;

FIG. 6 is a schematic illustration, with parts and portions removed, showing a strip of deformable material movable through progressive die stations leading to the formation of the end enclosure;

FIG. 7 is a view along line 77 of FIG. 6, partly in section and with elements added for purposes of clary;

FIG. 8 is a view along line 8-8 of FIG. 6, further illustrated in the same manner as FIG. 7;

FIG. 9 is a view along line 9-9 of FIG. 6, further illustrated in the same manner as FIG. 7;

FIG. 6A is a schematic illustration similar to the view of FIG. 6, but showing additional progressive die stations which complete the formation of the end enclosure;

FIG. 10 is a view along line 10-10 of FIG. 6A, on an enlarged scale, partly in section, and with elements added for purposes of clarity;

FIG. 11 is a view along line 11-11 of FIG. 6A, and further shown in the same manner as the view of FIG. 10;

FIG. 12 is a view along line 12-12 of FIG. 6A, and further shown in the same manner as the view of FIG. 10;

FIG. 13 is a view along line 13-13 of FIG. 6A, and further shown in the same manner as the view of FIG. 10; and

FIG. 14 is a view along line 14-14 of FIG. 6A, and further shown in thesame manner as the view of FIG.

The use of the same numerals in the different views of the drawings will indicate a reference to the same structures, parts or elements, as the case may be.

The improved end enclosure shown generally as 16 is seen mounted in a transformer 18 in the view of FIG. 1. The operable end enclosure separated from the transformer is shown in following FIGS. 2-4.

The end enclosure shown as having a flat top wall 20. A pair of opposed square corner sidewalls 22 are joined to the top wall along a bend line or square corner 24. Another pair of opposed round corner sidewalls 26 are joined to this top wall by a round corner or bend line 28 which is formed along a radius.

Eachsidewall is shown with an adjoining flange portion, such as square corner sidewall flanges 30, which are formed along a bend line 31 so that such flanges are substantially perpendicular to the plane of the adjoining sidewall. The round comer sidewalls 26 also have a round corner sidewall flange similarly disposed along a bend line 33.

A plurality of elongated openings 34 are shown in each sidewall. Through such openings, conductors 35 pass outside the transformer for connection to various electrical components. Each elongated opening is shown as having an upper, closed top 36, and an opposite, lower open bottom 38. The elongated opening is provided with an outwardly bent lip 40 which is customarily provided to keep the edges of the opening out of damaging contact with the insulation cover of the conductor 35. It will be seen that the plurality of elongated openings 34 in the square corner sidewalls 22 have their closed ends right up to square corners or bend lines 24. It will further be seen that the closed ends of elongated openings 34 in the round comer sidewalls 26 are positioned within the formed corner radius or bend line 28. The open ends 38 of the respective elongated openings are shown positioned in the various flange portions adjoining the respective sidewalls.

The opposite ends of the square corner sidewalls 22 are shown with locking tab extensions 42. In the assembled enclosure, the tabs are bent to overlap the opposite ends of the round corner sidewalls 26, as shown. Such locking tabs 42 form a part of an efficient interlock between the respective sidewalls, as will be shortly described in greater detail. The overlapping extension tabs 42 retain round cornered sidewalls 26 from being displaced outwardly or away from each other. The round comer 28 also imparts added rigidity to counter any tendencies of round corner sidewalls 26 from being displaced towards or away from each other.

The end enclosure shown in the foregoing views is formed from the cutout blank sheet of deformable material shown in the view of FIG. 5. Such a planer blank has a pair of opposite square corner sidewall portions 22, and another pair of opposite round corner sidewall portions 26, both extending in normal relationship to central top wall portion 20. The square corner sidewall portions 22 are moved along square corner bend line 24 so that they lie in planes which are normal to the plane of the top wall portion 20. The round corner sidewall portions 26 are moved downwardly to form curved bend line 28, such round cornered sidewalls also lying in a plane which is normal to the plane of the top wall portion 20.

In the illustrated view of FIG. 5, flange portions 30, at the bottom of square corner sidewall portion 22, are bent outwardly along bend lines 31 so that such flange portions are substantially perpendicular to the sidewall portions. In the same way, flange portions 32 on the round corner sidewalls are moved along bend lines 33 to be similarly fashioned. It is seen that flange portions 32 along sidewal portions 26 extend beyond the opposite ends of the round corner sidewalls a distance equivalent to the thickness of flange portions 30. As a result, the assembled end enclosure forms a substantially continuous flange portion at the bottom of the respective sidewalls, interrupted only by the open ends 38 of the elongated openings 34.

The interlock in the formed end enclosure is enhanced by features inaddition to locking tabs 42. The round corner sidewalls 26 have opposite ends 44 which are inboard of shoulders 45. The straight corner sidewalls 22 have upper opposite arcuate corners 46 which are inboard of lower opposite straight corners 47. In assembled form, this inside-outside position prevents inward displacement of the respective sidewalls, whereas the locking tabs prevent outward displacement of the round corner sidewalls. The frictional contact of the locking tabs 42 against the round corner sidewalls also helps to prevent outward displacement of square corner sidewalls 22, that is, away from each other.

It will be apparent that the blank cutout shown in FIG. 5 can be variously cut out by removing areas of selected configurations from four corners of a sheet of deformable material such as rolled steel. Following the removal of such configurations, the resulting blank shown in FIG. 5 can be assembled by moving the square corner sidewalls downwardly to the desired position, then moving the round corner sidewalls downwardly to the desired position where the opposite ends adjoin the opposite ends of the square corner sidewalls. The upper arcuate corner 66 are then positioned inside the shoulders 45, and the lower most straight corners 47 are positioned outside the ends 44. The tab extensions 42 are then bent towards each other to overlap the end 44 of the round corner sidewalls. Flange portions 30 and 32 are then bent outwardly until they are substantially perpendicular to the planes of their adjoining sidewalls.

The improved end enclosure is likewise adapted for rapid automated production by a continuous method such as that shown in following views of FIGS. 6-14. Looking first at FIGS. 6 and 6A, various progressive die stations are indicated by Roman numeral designations. A strip of deformable sheet material is continually advanced in a direction indicated to the right of the views of FIGS. 6 and 6A. The illustrated strip is used to make two enclosures simultaneously, one or each side of a center carrier strip indicated at 50. One lateral strip formation is indicated at A, and this strip formation shall be referred to for purposes of a detailed description, although it should be understood that the same structures, elements and parts occur simultaneously on a strip formation partly shown and indicated at B. The entire strip may therefore be considered as being bilaterally symmetrical, that is, along the longitudinal axis of common carrier strip 50.

A blank cutout station is generally at I. The areas of selected configuration are removed at this station from the blank sheet material to form a blank of extending sidewall portions. A slotting station is indicated II where elongated slots are formed in the respective sidewall portions. A first lip forming station is shown at III, and this initially forms a lip around the elongated openings in the sidewall portion. A lancing station is shown at IV wherein strip portions are separated so that the transverse wall portions may be moved into position to form the end enclosure. The lip formation is completed at station V where the curve is desirably flared, and where an interlocking element is also moved into position. A partial formation of the sidewalls is indicated at the partial form station VI. A final form round corner sidewall station is indicated at VII, and an inside forming station indicated at VIll form forming a round corner sidewall adjacent the common carrier strip 50. The

square corner sidewalls are completed at a final form station indicated by IX. The finally formed end enclosure is then separated from the carrier strip 50 at cutoff station X.

The sheet of deformable material is advanced between an upper die component collectively indicated at 52 and a lower die component collectively indicated at 54. Some of these components may be more particularly identified, but they generally shall represent the type of components operating in progressive die assemblies. Such components are variously actuated by conventionalmeans which will not'be described. The structural features of the die components will likewise not be particularly described, since the practitioners will readily understand such features from considering the formations at the various stations. The strip of advancing material shown in FIGS. 6 and 6A are illustrated without the upper and lower die components, but it is understood that such components are present as indicated somewhat in the partly sectioned views.

In the blank cutout station notched area 56 and cutout area 58 of selected configuration are formed by removing the pieces. A forming element shown as a cutout punch 59 removes a knockout piece 60. An appropriately formed die element which is not shown will likewise knockout a piece to form the cutout area 58.

The advancing strip is selectively positioned at the respective stations by means such as pilot location holes 61 which are engaged by pilot tubes, portionally indicated at 62. It is seen that repeated removal of areas 56, 58 results in formation of sidewall portions extending from an extending top-wall portion. It is further seen that the illustrated embodiment, round corner sidewall portions 26 extend in a direction which is normal to the direction of travel of the advancing strip. Cutout areas have formed the flange portion 32 which is freely positioned at the bottom of one of the round corner sidewalls 26. The opposed round corner sidewall is joined to the common carrier strip 50, and such wall is formed, except for the flange portion, by cutout areas 58.

The cutout areas 56 and 58 also form web portions 63 which have two, undivided square corner sidewall portions. The undivided square corner sidewall portion are in mutual mirror orientation with respect to their adjoining bottom edges which are not, however, separated at this station. The web portion 63 advances in a direction coincidental with the direction of the advancing strip.

Slotting station II forms the elongated openings in the respective sidewall. Cutouts 64 are seen in the round corner sidewall, and cutouts 65 are seen in the square corner sidewalls. The cutouts in the round corner and square corner sidewalls are formed by punch elements 66, 67. It will be seen that cutouts 64 are enlarged to a double cutout configuration 68 when the web portion 42 advances through the slotting station. Punch elements similar to 66 or 67 are used to punch the cutouts in reverse relationship to the cutout 64 so the resulting double cutout 68 is formed as shown. When such web portion is separated along a generally central line, the double cutout 68 will be symmetrically bisected to form elongated openings in each of the two separated round corner sidewalls. It will be seen that the elongated openings have a reduced width portion 69, such as on cutout 64,65; and such as is present at both opposite ends in cutouts 68. This reduced portion will be later opened up to substantially the same width as the larger cutout dimensions following a curling step wherein the rolled back sheet material will be in the form of a lip 40.

Station Ill illustrates the curling operation. A curl punch element 70 operates as a lower component to initially form a substantially straight curl 71 extending from the plane of the web portion 63. A similar punch element 73 forms a like straight curl 71 in the paired elongated openings 65 and 69. At the following station IV, the double round corner sidewalls in the web portion 63 are separated by a lancing or cutting step. The lance die component 75 cuts the web portion so that the round comer sidewalls separate along separation line 74.

In the following station V, the straight curls are completely formed by punch element 78 which turns the straight curl over at rounded corners to flare or to form the lip 40 as it finally appears in the assembled end enclosure. At the same station, the locking tabs 42 are bent back so they are in a plane which is normal to the square corner sidewalls and parallel to the rounded corner sidewalls. Tab bending punches 80 with right angle faces are used to turn the locking tabs into said bent position.

Following station VI is a partial sidewall forming station in which a flange and sidewall punch 82 with a right angle dihedral face 84 forms the flange poritons 32, and partially bends both square corner sidewalls and the free round corner sidewall. The round corner sidewall fixed to the common carrier strip 50 is formed at a later station.

One of the round corner sidewalls is formed at station Vll by the round corner sidewall punch 86 having an arcuate forming face. Such punch completes the movement of the sidewall from the partially turn position to the finally moved and formed position as indicated in the view of FIG. 11.

The opposite round corner sidewall is formed at following station VIII by inside sidewall punch 88, which has an outside corner radius that cooperatively acts with corresponding inside corner radius of the upper component 52 to form the round corner of the sidewall.

The opposite square corner sidewalls are fashioned in the final form station IX by square corner sidewall punches 90 which have right angle faces for this purpose, The partially moved sidewalls 28 are completely moved to their final position where they lie in plane substantially normal to the top wall portion 20.

The final station X is the cutoff station which separates the completed, assembled end enclosure from the carrier strip by action of cutoff punch 92. Such punch 92 separates a knockout piece 94 from the common carrier strip 50 to simultaneously form flanges 32 and to drop the completed end enclosures into a receptaclw, not show.

The claims of the invention are now presented.

What is claimed is:

1. A method for forming an end enclosure for transformers, which includes the steps of removing areas of predetermined configurations from four corners of a planer, deformable sheet material to thereby obtain first and second pairs of opposite sidewall portions, said first pair being disposed in substantially normal relationship to said second pair, said sidewall portions extending from a central top wall portion moving said paired, opposite sidewall portions along bend line to one side of said top wall portion so said sidewall portions lie in planes substantially normal to said top wall portions,

forming the bend line of one pair of opposite sidewalls as square corners,

bending lower portions of each sidewall to form a flange portion extending outwardly in perpendicular relation to said sidewall, and

forming at least one elongated opening in each of the opposite pair of square corner sidewalls, said opening having a closed end at the square corner bend line and an opposite end extending to at least the flange adjacent said square corner sidewall.

2. A method for forming an end enclosure for transformers as in claim 1, which further includes forming the bend line of the other opposite pair of sidewalls along a radius to obtain round corners and thereby strengthen said round cornered sidewalls against displacement.

3. A method for forming an end enclosure for transformers as in claim 2, which further includes forming an interlock between opposite ends of adjacent sidewalls, said interlock operating to prevent inward displacement of the square cornered sidewalls towads each other, and further operating to prevent outward displacement of the round cornered sidewalls away from each other.

4. A method for forming an end enclosure for transformers as in claim 3, wherein said interlock is formed by a step of extending locking tabs from each opposite end of the square corner sidewalls, and further forming upper opposite corners of the square corner sidewalls on a radius complementary to the radius of the round corner sidewalls, fitting said upper opposite corners inside the radius of said round corner sidewalls when said sidewalls are moved into planes positioned substantially normal to said top wall.

5. A method for forming an end enclosure for transformers as in claim 4, wherein said opposite lower corners of the square corner sidewalls are formed as straight edges, and extending such straight edges beyond the upper opposite corners of said square corner sidewalls so that said lower opposite corners are outside the opposite of the said round corner sidewalls.

6. A method for forming an end enclosure for transformers as in claim 5, which includes extending the flange portions of one pair of opposite sidewalls beyond their opposite ends a distance substantially equal to the width of the flange portion, and forming the flange portions of the other pair of sidewalls coextensively with the opposite ends of said other pair of sidewalls, so that the respective flange portions form a substantially continuous flange along the bottom of the sidewalls following movement of said sidewalls into planes positioned substantially normal to said top wall.

7. A method for forming an end enclosure for transformers as in claim 6, which includes forming a plurality of elongated openings in one pair of opposite sidewall portions which extend from the central top wall portion in the planar deformable sheet material, forming said elongated opening with an upper closed end and a bottom open end at the bottoms of said opposite sidewall portions, forming the bend line of said sidewall portions as square corners substantially coincidental with the closed ends of said elongated opening, and bending the lower portions of each of said opposite sidewalls to form the outwardly extending flanges with the open ends of said elongated openings disposed therein.

8. A method for forming an end enclosure for transformers as in claim 7, which further includes forming a plurality of elongated openings in the other pair of sidewall portions extending from said central top wall portion in the planar, deformable sheet material, said elongated opening having an upper closed end and a bottom open end at the bottom edge of said sidewall portions, and forming the bend lines of said other pair of opposite sidewall portions along a radius so that the closed ends of said elongated slots are within the curve of said radius.

9. A method for forming an end enclosure for transformers as in claim 1, wherein said planar, deformable sheet material is in the form of an elongated strip,

said strip being advanced through progressive die stations, including a blank cutout station where the areas of predetermined configurations are punched out,

a slotted station where the elongated openings are formed with portions of reduced width by removing sheet material,

a curling station wherein sheet material at the reduced width portions are moved to form a lip,

a partial sidewall forming and flange forming station wherein at least one pair of opposite sidewall portions are partially moved downward from the plane of the top wall portion, and wherein the flange portion is formed substantially perpendicular to its wall portion by a forming element with a right angle dihedral face,

a square comer forming station wherein forming elements move the one pair of sidewall portions into planes substantially normal to the top wall portion and also form the square corners,

a final sidewall forming station wherein forming elements complete the formation of sidewall movement to a point substantially normal to the top wall, and

a cutoff station where the formed end enclosure is separated from the advancing material strip.

10. A method for forming an end enclosure for transformers as in claim 9, wherein removal of areas of predetermined configurations at the blank cutout station result in one pair of planar opposite wall portions extending in normal relationship to the direction of travel of the advancing strip, one of said pair of planar wall portions being carried by an advancing carrier strip pair of planer wall portions to another adjoining pair of wall portions likewise extending in a direction normal to the direction of travel, said web portion comprising two like, undivided wall portions in mirror relationship, one of said undivided wall portions being part of a following pair of opposite wall portions of the strip, and the other of said undivided wall portions being part of the leading opposite wall portions of the strip.

11. A method for forming an end enclosure for transformers as in claim 10, wherein said elongated openings are formed by punching out areas in the opposite wall portions which are normal to the direction of travel of the advancing strip, forming an open end in said opening at the free end flange portion, punching out said openings as enclosed areas in the opposite wall portions which are joined to the carrier strip, and punching out elongated openings in said web portion as double openings with opposite, reduced width portions.

12. A method for forming an end enclosure for transformers as in claim 11, which further includes cutting said web portion with a lanching element at a lance station into two bilaterally symmetrical parts on each side of the cut, separation line.

13. A method for forming an end enclosure for transformers as in claim 12, wherein said carrier strip carries deformable sheet material on each side, and wherein progressive die stations form enclosures on both sides as the strip advances through said stations.

14. A method for forming an end enclsoure for transformers as in claim 13, wherein said pair of opposite wall portions extending in a direction normal to the direction of travel of the advancing strip are formed into square corner sidewalls at said square corner forming station, and wherein said pair of opposite wall portions traveling in the direction of the advancing strip are formed into round corner sidewalls at a round corner forming station by forming elements having a face formed on a radius.

15. A method for forming an end enclosure for transformers as in claim 14 wherein said carrier strip has a plurality of pilot locations therealong and wherein pilot elements engage said pilot locations to fix the advancing strip at the various stations for the forming operations. 

1. A method for forming an end enclosure for transformers, which includes the steps of removing areas of predetermined configurations from four corners of a planer, deformable sheet material to thereby obtain first and second pairs of opposite sidewall portions, said first pair being disposed in substantially normal relationship to said second pair, said sidewall portions extending from a central top wall portion moving said paired, opposite sidewall portions along bend line to one side of said top wall portion so said sidewall portions lie in planes substantially normal to said top wall portions, forming the bend line of one pair of opposite sidewalls as square corners, bending lower portions of each sidewall to form a flange portion extending outwardly in perpendicular relation to said sidewall, and forming at least one elongated opening in each of the opposite pair of square corner sidewalls, said opening having a closed end at the square corner bend line and an opposite end extending to at least the flange adjacent said square corner sidewall.
 2. A method for forming an end enclosure for transformers as in claim 1, which further includes forming the bend line of the other opposite pair of sidewalls along a radius to obtain round corners and thereby strengthen said round cornered sidewalls against displacement.
 3. A method for forming an end enclosure for transformers as in claim 2, which further includes forming an interlock between opposite ends of adjacent sidewalls, said interlock operating to prevent inward displacement of the square cornered sidewalls towads each other, and further operating to prevent outward displacement of the round cornered sidewalls away from each other.
 4. A method for forming an end enclosure for transformers as in claim 3, wherein said interlock is formed by a step of extending locking tabs from each opposite end of the square corner sidewalls, and further forming upper opposite corners of the square corner sidewalls on a radius complementary to the radius of the round corner sidewalls, fitting said upper opposite corners inside the radius of said round corner sidewalls when said sidewalls are moved into planes positioned substantially normal to said top wall.
 5. A method for forming an end enclosure for transformers as in claim 4, wherein said opposite lower corners of the square corner sidewalls are formed as straight edges, and extending such straight edges beyond the upper opposite corners of said square corner sidewalls so that said lower opposite corners are outside the opposite of the said round corner sidewalls.
 6. A method for forming an end enclosure for transformers as in claim 5, which includes extending the flange portions of one pair of opposite sidewalls beyond their opposite ends a distance substantially equal to the width of the flange portion, and forming the flange portions of the other pair of sidewalls coextensively with the opposite ends of said other pair of sidewalls, so that the respective flange portions form a subStantially continuous flange along the bottom of the sidewalls following movement of said sidewalls into planes positioned substantially normal to said top wall.
 7. A method for forming an end enclosure for transformers as in claim 6, which includes forming a plurality of elongated openings in one pair of opposite sidewall portions which extend from the central top wall portion in the planar deformable sheet material, forming said elongated opening with an upper closed end and a bottom open end at the bottoms of said opposite sidewall portions, forming the bend line of said sidewall portions as square corners substantially coincidental with the closed ends of said elongated opening, and bending the lower portions of each of said opposite sidewalls to form the outwardly extending flanges with the open ends of said elongated openings disposed therein.
 8. A method for forming an end enclosure for transformers as in claim 7, which further includes forming a plurality of elongated openings in the other pair of sidewall portions extending from said central top wall portion in the planar, deformable sheet material, said elongated opening having an upper closed end and a bottom open end at the bottom edge of said sidewall portions, and forming the bend lines of said other pair of opposite sidewall portions along a radius so that the closed ends of said elongated slots are within the curve of said radius.
 9. A method for forming an end enclosure for transformers as in claim 1, wherein said planar, deformable sheet material is in the form of an elongated strip, said strip being advanced through progressive die stations, including a blank cutout station where the areas of predetermined configurations are punched out, a slotted station where the elongated openings are formed with portions of reduced width by removing sheet material, a curling station wherein sheet material at the reduced width portions are moved to form a lip, a partial sidewall forming and flange forming station wherein at least one pair of opposite sidewall portions are partially moved downward from the plane of the top wall portion, and wherein the flange portion is formed substantially perpendicular to its wall portion by a forming element with a right angle dihedral face, a square corner forming station wherein forming elements move the one pair of sidewall portions into planes substantially normal to the top wall portion and also form the square corners, a final sidewall forming station wherein forming elements complete the formation of sidewall movement to a point substantially normal to the top wall, and a cutoff station where the formed end enclosure is separated from the advancing material strip.
 10. A method for forming an end enclosure for transformers as in claim 9, wherein removal of areas of predetermined configurations at the blank cutout station result in one pair of planar opposite wall portions extending in normal relationship to the direction of travel of the advancing strip, one of said pair of planar wall portions being carried by an advancing carrier strip portion and the opposite wall portion being freely carried with a flange portion formed thereon, the other pair of planer wall portions exending in a direction coincidental with the direction of travel of the advancing strip and being part of web portions joining the first pair of planer wall portions to another adjoining pair of wall portions likewise extending in a direction normal to the direction of travel, said web portion comprising two like, undivided wall portions in mirror relationship, one of said undivided wall portions being part of a following pair of opposite wall portions of the strip, and the other of said undivided wall portions being part of the leading opposite wall portions of the strip.
 11. A method for forming an end enclosure for transformers as in claim 10, wherein said elongated openings are formed by punching out areas in the opposite wall portions which are normal To the direction of travel of the advancing strip, forming an open end in said opening at the free end flange portion, punching out said openings as enclosed areas in the opposite wall portions which are joined to the carrier strip, and punching out elongated openings in said web portion as double openings with opposite, reduced width portions.
 12. A method for forming an end enclosure for transformers as in claim 11, which further includes cutting said web portion with a lanching element at a lance station into two bilaterally symmetrical parts on each side of the cut, separation line.
 13. A method for forming an end enclosure for transformers as in claim 12, wherein said carrier strip carries deformable sheet material on each side, and wherein progressive die stations form enclosures on both sides as the strip advances through said stations.
 14. A method for forming an end enclsoure for transformers as in claim 13, wherein said pair of opposite wall portions extending in a direction normal to the direction of travel of the advancing strip are formed into square corner sidewalls at said square corner forming station, and wherein said pair of opposite wall portions traveling in the direction of the advancing strip are formed into round corner sidewalls at a round corner forming station by forming elements having a face formed on a radius.
 15. A method for forming an end enclosure for transformers as in claim 14 wherein said carrier strip has a plurality of pilot locations therealong and wherein pilot elements engage said pilot locations to fix the advancing strip at the various stations for the forming operations. 